sonyxperiageek:frankv: Without knowing vhat you're interested in, it's hard to advise.
Google Maps tends to be generous with travel time... 8 hours total is probably about right for Auck-Wgtn.
Aim to get petrol at Tokoroa BP... cheapest on SH1, I believe.
Butter Factory cafe at Waharoa on SH27 is nice.
Stop at Huka Falls for a short walk to the falls, or a jet boat ride. Picnic lunch at one of the rest areas along Lake Taupo if the weather is sunny. Taihape has a couple of decent cafes.
In Wellington, drive round the coast Island Bay to Evans Bay, stopping at Moa Point for some aircraft to land. Te Papa. Dowse Art Gallery in Lower Hutt. Paekakariki Hill lookout. Eastbourne is a nice outing on the ferry. Paekakariki Hill lookout. Southwards Car Museum at Paraparaumu. I'm told that the Roxy cinema in Miramar is a must-see. Parliament Buildings. A movie at the Embassy Cinema.
I think that's a bit early in the trip to get petrol. The car should be able to last one way there on a tank of fuel, but will keep your suggestion in mind.
If you have long range tanks you could make it however given the time of year and delays especially between Otaki to to Wellington you should top up at say Bulls.